All the following is translated from the Japanese-language blog of Feastrex's president -- Chris

"More thoughts after listening to the new D9e-III one-off special model"

I got my Ph.D. in biotechnology, not in an audio-related field. To the extent that I can speak authoritatively about audio, it is on the basis of my extensive experience as a seriously dedicated user, rather than as someone possessing extensive knowledge about the theoretical aspects of audio.

Right now the D9e-III one-off special model playing in our listening room until June 8 is teaching me many new and exciting things about the capabilities of fullrange drivers, and (for me at least) it is driving some more nails into the coffin of some mistaken ideas that seem to be generally regarded as true in the world of audio.

For example, I have frequently heard it said that reducing the moving mass of a cone transducer (i.e., making it lighter) makes it more difficult to produce deep bass. But this latest pair of drivers, with a cone diameter of 21cm and a moving mass of 8g, is not only able to produce bass of better quality than any of the 38cm woofers that I have owned (and I have owned many, including some costing thousands of dollars apiece), in the music that I have been throwing at these drivers I cannot find a single instance in which my various 38cm drivers could outperform these fullrange drivers in any respect.

The "flip side" of the coin that says a heavy cone is desirable for deep bass says that a powerful motor gives a rising frequency response. However, that too is not borne out by my listening, although perhaps this enclosure has something to do with it. (This is just a simple box that we cobbled together from what we had on hand and I'm sure it is far from ideal, and yet the driver still sounds better than anything else I have ever heard in my life.) The Type III field coil driver has an actual gap flux density of 22,800 gauss at the field coil voltage we are using, and the tonal balance of the driver is superb. The quality of the highest frequencies seems to our ears to be in no way inferior to any of our 5-inch drivers. If ever a driver deserved to be called a fullrange driver, this is it. (Too bad it's so expensive, on account of all that Permendur in the motor.)

What this driver is telling me is that if you use really good materials and design and build the driver well, you can still get awesome bass and a great overall tonal balance from a fairly small diameter, lightweight cone.

I have also heard it said that a high-resolution transducer will tend to sound thin, but with this driver nothing could be further from the truth. The more faithfully the transducer can reproduce the input signal, the richer and more musically expressive the sound output should become. These new drivers prove that to be the case, beyond any shadow of a doubt.

More than ever, in listening to these drivers I am left in awe of the paper specially made for us by living national treasure Ichibei Iwano. If you can imagine how Stradivarius must have felt about a favorite source of tonewood or varnish compound for his instruments, you'll understand how I feel about Mr. Iwano's paper. This paper is the most ideal material for building the main cones of fullrange drivers that I have ever encountered. Nothing else even comes close.

Together with the excellent materials used in the diaphragm, I think these new drivers shows the benefits of a powerful motor. Our field coil motor, which weighs 12kg, would be considered very powerful even on a 38cm woofer. (There are some high-grade 38cm woofers with motors this powerful.) But these fullrange drivers have about 1/3 the cone area and perhaps 1/12 the moving mass of a typical high grade 38cm woofer, so the great power of the motor relative to the cone should be readily apparent. Thinking in terms of an automobile engine, our engine has both high horsepower and high torque.

Our drivers have numerous other unusual features as well, so I don't know the exact reason why, but one veteran speaker designer who has been working with our drivers in Japan recently has said that the standard parameter-based design formulas that he has been using successfully over the years are less useful for working with our drivers than with any other fullrange drivers that he has encountered thus far. He said that to us after comparing his own preliminary designs to our own simple enclosure designs arrived at through repeated cut-and-try. He said he always expects to modify a design a few times before he gets it right, but he says that with our drivers doing things "by the book" (his book, at any rate) seems to hobble some of the driver's inherent capabilities rather than unleashing them. He is now back at his drawing board and doing further experimentation to eliminate the bottlenecks in his design.

Difficult to use? Personally, I don't think so. In the beginning it took us a while to find a box that we thought worked really well, but it turned out that some ridiculously simple boxes give excellent results, at least to our ears. Recently we are once again experimenting with some slightly more complicated designs, but they are still relatively simple and straightforward to build. There may be much more sophisticated enclosure designs possible that would give even better results, but I bet anyone trying to design such enclosures is going to do a lot of old-fashioned cut-and-try work before they are fully satisfied. In the meantime, these drivers are just sitting in these thrown-together boxes playing the most incredible music you've ever heard, like there's no tomorrow.

One of our D9e-II drivers (dimensionally essentially the same as the D9e-III drivers that I have been discussing) shown next to a JBL D-130 38cm broadband driver for comparison.

Total mass of 6kg versus 12kg for the D9e-III's motor.

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"Avoiding deportation from Japan for over a quarter century!"

Joe,
Thanks again for the prompt reply to my e-mail through your website yesterday, and it's a holiday long weekend in the US also, so thanks..

This is great news to me as I was saving up over the next many months for a pair of AER MK1 drivers, but the entry Feastrex drivers are not much more per pair I see now, ( could still be a bit less though ).

I had thought a pair of the cheapest drivers were over 5grand, way out of my budget, but I think now my choice has been made I guess there isn't anyone selling the drivers in Canada yet?, the duty and shipping will add up a fare bit too I guess..

Looking forward as I save up to reading many more reviews of these special wonders and the different enclosures used etc..
Dave

The Lotus Group services Canada as well as the USA. The shipping will not be that great as we will ship via the Post Office unless you have an alternate preferred method. You can always call to discuss the particulars when the time is right.

All the following is translated from the Japanese-language blog of Feastrex's president -- Chris

that must've taken a lot of time

as my wife is a professional translator, I appreciate your meaning-based translation. The doctor's passion and his musings about the driver are nicely conveyed. Good translation helps us to peer deeper into the mind and heart of a fellow audiophile-- despite the language barrier.

thanks, Chris

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Disclaimer: I may or may not offer for sale items mentioned in this thread, and if I do, I may or may not make a profit.

Here is the naked truth:
One listener's comment after returning home and listening to his current system: "I thought I had a pretty good audio system but after listening to those Feastrex drivers, my current system sounds like a portable AM radio by comparison."

Here are the three D9e models side by side. Keep in mind that the D9e-III with bronze frame is a special one-off and that normally the driver would have a black frame like the other two drivers shown.
I'm pretty sure the phase plug shown with the Type III driver is a bronze phase plug that has been painted with urushi lacquer.

-- Chris

__________________
"Avoiding deportation from Japan for over a quarter century!"

Just announced at the president's blog: the new NF5ex field coil driver:

(the above is an early prototype; the actual field coil is a good deal larger)

The last image is showing the temperature of the driver (C) at 15V input voltage.

This is Feastrex's entry level 5-inch field coil driver. I have not heard it myself, but everyone who has heard it has been impressed. Although still expensive I hear that the price is going to be almost half that of the D5e-I field coil driver, which was previously the cheapest field coil driver that Feastrex offered.

Anything that gets the price down while keeping quality up is a step in the right direction, I'd say! And yes, the much more expensive D5e family does sound even better (I am told), so it is not as if this driver has made any other Feastrex driver obsolete.

-- Chris

__________________
"Avoiding deportation from Japan for over a quarter century!"